Plastic implant for osteosynthesis

ABSTRACT

The invention relates to an osteosynthesis implant ( 1 ) that preferably consists of a bioresorbable plastic material. The inventive implant receives the longitudinal fixation elements ( 10 ) to be anchored in the bone, especially in the form of wires, nails, pins or screws. The openings destined to receive the fixation elements ( 10 ) do not completely extend through the implant ( 1 ) like in conventional bone plates or intramedullary nails but are degenerated to indents ( 2 ) in the surface of the implant ( 1 ) so that they may serve as a guide for the fixation elements ( 10 ) to be guided through the implant ( 1 ). The inventive implant ( 1 ) allows insertion of the fixation elements ( 10 ) in the bone diverging angles and crossing one another, so that the fixation elements ( 10 ) extending intramedullarly or in the spongiosa are primarily prevented from migrating in a proximal or distal direction.

[0001] The invention relates to a plastic implant for osteosynthesisaccording to the preamble of claim 1 as well as a fixation device withsuch an implant according to the preamble of claim 17.

[0002] The implant can be formed as a bone plate or an intramedullarynail. In its plate-like embodiment it can act as an internal fixationmeans for osteosynthesis, for example, to the proximal humerus or otherareas near the joint of tubular bones.

[0003] From U.S. Pat. No. 5,476,467 BENOIST, a guiding template that hasshafts in the manner of a fan is known for guiding Kirschner wires. Thedisadvantages of this arrangement consist of the fact that the fixationelements (Kirschner wires) can only be guided parallel to one anotherthrough the guiding template. Due to the shaft structure of thetemplate, it does not lie directly on the bone so that the length of thewires to be introduced is unnecessarily extended.

[0004] Here the invention aims to provide a remedy. The objective of theinvention is to provide an osteosynthetic implant which has nopenetrating holes to receive longitudinal fixation elements to beanchored in the bone, but rather only a number of indentations in itssurface that serve as an aid to positioning and guiding to introduce thefixation elements, at diverging angles and crossing one another, firstthrough the implant and then into the bone.

[0005] The implant permits the introduction of Fixation elements, atdiverging angles and crossing one another, into the bone so thatprimarily a migration of the fixation elements running intramedullarilyor in the spongiosa is preventing proximally as well as distally.

[0006] The invention realizes the objective set with an implant that hasthe features of claim 1 as well as a fixation device that has thefeatures of claim 17.

[0007] The indentations, preferably formed conically or cylindrically,in the upper side of the implant serve as centering elements for thepenetrating holes of the guiding plate, for example, with Kirschnerwires. The Kirschner wires have, on their front part, a drill bit whoselength corresponds preferably to at least the thickness of theplate-like implant or to the diameter of the implant in the form of anintramedullary nail. Furthermore, the Kirschner wires have an outerthread that serves to secure against axial displacement in the implantso that a migration of the Kirschner wires in the implant is prevented.The Kirschner wires can be drilled into the implant at angles to itssurface that can be freely chosen by the surgeon, preferably indirections skewed relative to one another in order to achieve an optimalfracture fixation. The position and angle of the Kirschner wires canthus be chosen according to the fracture to be cared for.

[0008] Thus the advantage can be achieved that a minimally invasiveoperation technology can be applied, with implant material to beinserted minimally. The implant according to the invention is suitablein particular, due to the possibility of arranging the fixation elementsin three dimensions, to osteosynthesis of bones that are osteoporotic orweakened by disease. The stability of the osteosynthesis is thusproduced primarily by the bolts/wires and their crosswise positioning inthe bone. Due to the fact that the implant lies directly on the bone,the free length of the wires to be introduced is reduced to a minimum.Thereby an early load of the fracture site is possible, and thus anearlier utilization of the affected connective masses and, in the idealcase, quicker healing.

[0009] A preferred extension consists of the case wherein the implantconsists of a bioresorbing or biodegradable plastic that is preferablychosen from the group of polylactates. The indentations are expedientlydisposed in a regular grid on the upper side of the implant.

[0010] In a development as a bone plate or as plate-like guiding bodies,the implant preferably has an approximately circular upper side withindentations disposed in concentric circles. The number of indentationsis between 3 and 100, preferably between 7 and 40. Typically 10indentations are provided. Expediently the indentations expand conicallytoward the upper side. The conical indentations advantageously have aconical angle ranging from 30° to 120°, preferably from 40° to 100°. Theindentations have on the upper side a diameter ranging from 1.0 to 3.0mm, preferably between 1.5 to 2.2 mm (typically 2 mm). The depth of theindentations is in the 0.6 to 1.5 mm range, preferably between 0.8 to1.2 mm (typically 1 mm).

[0011] In the preferred embodiment as plate-like implant, its upper sideis preferably formed convexly in order to achieve a better conformity tothe surface of the bone. Its thickness is in the 2 to 6 mm range,preferably between 2.5 to 4.0 mm. The upper side expediently has asurface area ranging from 3 to 15 cm², preferably between 4 to 10 cm²(typically 4.5 cm²).

[0012] In a preferred form of embodiment, the fixation element used asimplant has a drill bit with a length from 4 to 10 mm, preferably from 5to 8 mm. The drill bit should preferably correspond at least to thethickness of the implant.

[0013] The fixation element is expediently provided with an outerthread, preferably over a length from 30 to 80 mm. It preferably has nohead at its back end and has a uniform diameter, seen over its entirelength, preferably in the 1 to 6 mm range (typically in the 2 to 5 mmrange).

[0014] The invention and extensions of the invention are explained inmore detail in the following with the aid of the partially schematicrepresentations of an embodiment example. Shown are:

[0015]FIG. 1 a perspective representation of a plate-like implant formedas a guiding body,

[0016]FIG. 2 a cross-section through the implant along the line II-II inFIG. 1 in the area of two indentations,

[0017]FIG. 3 a view of a fixation element in the form of a Kirschnerwire, and

[0018]FIG. 4 a view of a fractured humerus with an implant that isfastened to the bone with a plurality of Kirschner wires drilledtherein.

[0019] The implant 1 represented in FIGS. 1 and 2 consists of a3-mm-thick, arched plate of a biodegradable plastic, in particular apolylactate, suitable for implantation in the human body. The implant 1has a convex upper side 3 and a concave lower side 4 intended forcontact with the bone. In the upper side 3 a plurality of indentations 2in the form of funnels expanding conically toward the upper side 3 areintroduced.

[0020] The lower side 4 of the implant 1 is preferably made to conformto the bone surface to be applied in order to achieve as good and broada bone contact surface as possible.

[0021] Represented in FIG. 3, the fixation element 10 in the form of acustomary Kirschner wire has no head at its back end 13 so that it has auniform diameter over its entire length. At its front end the fixationelement 10 has a drill bit 11 as well as an outer thread 12.

[0022] The implant 1 can be introduced through a minimal incision in thebody, for example, in the area of the proximal humerus 20 (FIG. 4) towhich it can be fastened with the fixation means 10. In so doing, theadditional use of bone cement is not ruled out. Since the plate-likeimplant 1 has sufficient indentations 2, they can serve to fasten bandsto bone fragments of the humerus 20. In so doing, the three-dimensional,skewed arrangement of the fixation means 10 prevents their loosening sothat on the whole a greatly improved stability of fixation results.

1. Plastic implant (1) for osteosynthesis which serves to receivelongitudinal fixation elements (10), in particular in the form of wires,nails, pins, or screws, to be anchored in the bone characterized by thefact that the openings intended to receive longitudinal fixationelements (10) do not penetrate the implant (1) completely but rather arereduced to indentations (2) in the surface of the implant (1) so thatthey serve as an aid to positioning and guiding for the fixationelements (10) to be guided through the implant (1).
 2. Implant (1)according to claim 1, characterized by the fact that the plastic isbioresorbing and preferably chosen from the group of polylactates. 3.Implant (1) according to claim 1 or 2, characterized by the fact that itis formed as a plate with an upper side (3) and a lower side (4)intended for contact with the bone.
 4. Implant (1) according to claim 3,characterized by the fact that the indentations (2) are introduced atleast on its upper side (3).
 5. Implant (1) according to claim 3 or 4,characterized by the fact that the indentations (2) are disposed in aregular grid on the upper side (3).
 6. Implant (1) according to one ofthe claims 3 to 5, characterized by the fact that the implant (1)preferably has an approximately circular upper side (3) and theindentations (2) are preferably disposed in concentric circles. 7.Implant (1) according to one of the claims 3 to 5, characterized by thefact that the implant (1) has an oval or polygonal upper side (3). 8.Implant (1) according to one of the claims 3 to 7, characterized by thefact that the upper side (3) of the implant (1) is convex and the lowerside (4) is concave.
 9. Implant (1) according to one of the claims 3 to8, characterized by the fact that its thickness is between 2 to 6 mm,preferably between 2.5 to 4.0 mm.
 10. Implant (1) according to one ofthe claims 3 to 9, characterized by the fact that the upper side (3) hasa surface area in the 3 to 15 cm² range, preferably between 4 to 10 cm².11. Implant according to claim 1 or 2, characterized by the fact that itis formed as an intramedullary nail.
 12. Implant (1) according to one ofthe claims 1 to 11, characterized by the fact that the number ofindentations is between 3 and 100, preferably between 7 and
 40. 13.Implant (1) according to one of the claims 1 to 12, characterized by thefact that the indentations (2) extend conically toward the upper side(3).
 14. Implant (1) according to claim 13, characterized by the factthat the conical indentations (2) have a conical angle in the 30° to120° range, preferably from 40° to 100°.
 15. Implant (1) according toone of the claims 1 to 14, characterized by the fact that theindentations (2) have a diameter in the 1.0 to 3.0 mm range, preferablybetween 1.5 to 2.2 mm.
 16. Implant (1) according to one of the claims 1to 15, characterized by the fact that the depth of the indentations (2)is ranging from 0.6 to 1.5 mm, preferably between 0.8 to 1.2 mm. 17.Fixation device for bone surgery with an implant (1) according to one ofthe claims 1 to 16, characterized by the fact that it includes at leastone fixation element (10) for fastening the implant (1) on or in a bone.18. Fixation device according to claim 17, characterized by the factthat the fixation element (10) has a drill bit (11).
 19. Fixation deviceaccording to claim 18, characterized by the fact that the drill bit (11)has a length from 4 to 10 mm, preferably from 5 to 8 mm.
 20. Fixationdevice according to claim 18 or 19, characterized by the fact that thelength of the drill bit (11) corresponds at least to the thickness ofthe plate-like implant (1) or to the diameter of the implant (1) in theform of an intramedullary nail.
 21. Fixation device according to one ofthe claims 17 to 20, characterized by the fact the fixation element (10)is provided with an outer thread (12), preferably over a length from 30to 80 mm.
 22. Fixation device according to one of the claims 17 to 21,characterized by the fact that the fixation element (10) has no head atits back end (13).
 23. Fixation device according to one of the claims 17to 22, characterized by the fact that the fixation element (10) has auniform diameter, seen over its entire length.
 24. Fixation deviceaccording to one of the claims 17 to 23, characterized by the fact thatthe fixation element (10) has a diameter ranging of 1 to 6 mm,preferably of 2 to 5 mm.